Thermal Expansion Valve with Power Element

ABSTRACT

An improved power element for use with a thermal expansion valve. The power element contains a filter positioned at an open end of the power element to prevent debris from entering the body of the thermal expansion valve.

This application claims priority to U.S. Provisional Application 61/868,671 filed Aug. 22, 2013.

FIELD OF THE INVENTIONS

The inventions described below relate the field of thermal expansion valves and power elements for use with vehicle air-conditioning systems.

BACKGROUND OF THE INVENTIONS

In a typical automotive air-conditioning system, refrigerant is compressed by a compressor unit driven by the automobile engine. The compressed refrigerant, at high temperature and pressure, enters a condenser where heat is removed from the compressed refrigerant. The refrigerant then travels through a receiver/dryer to a thermal expansion valve. The thermal expansion valve throttles the refrigerant as it flows through a valve orifice, which causes the refrigerant to change phase from liquid to a saturated liquid/vapor mixture as it enters the evaporator. In the evaporator, heat is drawn from the environment to replace the latent heat of vaporization of the refrigerant, thus cooling the environmental air. The low-pressure refrigerant flow from the evaporator returns to the suction side of the compressor to begin a new cycle.

The thermal expansion valve regulates the rate at which liquid refrigerant flows into the evaporator. The controlled flow is necessary to maximize the efficiency of the evaporator while preventing excess liquid refrigerant from returning to the compressor.

The thermal expansion valve contains a power element that is located in the upper portion of the thermal expansion valve. The power element is filled with a volume of gas that changes as the temperature is sensed by the evaporator. The gas pressure inside the power element tends to open the thermal expansion valve. The power element is the upper portion of the thermal expansion valve, which is filled with gas that is mounted to the thermal expansion valve body. It is the key component in the function of the thermal expansion valve. Without the power element, the thermal expansion valve is not able to sense the temperature and pressure of the system. Once the thermal expansion valve stops metering the flow of refrigerant, the system does not produce the cooling effect.

Debris from the air-conditioning system leads to failure of the thermal expansion valve over time. The rate of failure is magnified when the thermal expansion valve is installed incorrectly upside down (power element to bottom). Debris from the air-conditioning system lands on the underside of the diaphragm of the thermal expansion valve and causes wear of the thermal expansion valve. The relatively thin diaphragm is forced over a small angular particle of debris and eventually causes a leak in the diaphragm. The leak ultimately causes the thermal expansion valve to become non-functional.

SUMMARY

The devices and methods described below provide for an improved power element for use with a thermal expansion valve. The power element is contained on the upper portion of the thermal expansion valve. The power element includes an annular domed upper housing and a mating annular lower housing. A diaphragm for sensing fluid pressure is mounted within a cavity formed by the upper and lower housing. The power element also includes a sleeve that passes through the opening in the bottom of the annular housing. The sleeve encloses a stem that is disposed within the sleeve and acts upon an operating pin. The operating pin moves the ball of a ball-type assembly for opening and closing an adjustment gland. In addition, a filter is interdisposed around the stem. The filter is positioned at an open end of the power element lower housing to prevent debris from entering the lower housing of the thermal expansion valve. The filter prevents the unwanted debris from entering the underside of the diaphragm of the thermal expansion valve. The filter assists in preventing entrance of unwanted debris when the thermal expansion valve is installed both upside down and right side up. The power element is secured to the top of a thermal expansion valve and the filter is positioned between the body of the thermal expansion valve and an open end of the power element, disposed within a flow path between the evaporator and a diaphragm chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a thermal expansion valve with a power element and filter.

FIG. 1 b is the thermal expansion valve of FIG. 1 a where the power element has moved the ball off the ball seat.

FIG. 2 is an exploded view of a power element of the thermal expansion valve.

FIG. 3 is a filter of the power element.

DETAILED DESCRIPTION OF THE INVENTIONS

FIG. 1 a illustrates a thermal expansion valve with a power element and filter. A thermal expansion valve 1 has a power element 2 located at the upper portion of the thermal expansion valve. The thermal expansion valve has a body 3 with an inlet port 4 and an outlet port 5. The inlet port is connected to the condenser of the vehicle air conditioning system so that refrigerant enters the thermal expansion valve via this port and creates a flow path from the condenser to the inlet port. The refrigerant exits the thermal expansion valve via the outlet port to the evaporator of the air conditioning system. The power element includes an annular domed housing which contains a diaphragm 7 within the annular domed housing. The annular domed housing has an upper 8 and lower 9 housing portion. A fluid path is defined between the evaporator and a diaphragm chamber defined between the diaphragm and the lower housing. A sleeve 10 extends from the bottom of the domed housing and a stem 11 is slidably disposed within the sleeve. The sleeve acts upon an operating pin 12. The thermal expansion valve also includes a ball-type assembly having ball 13 and an angled ball seat 14.

Connection of the power element 2 and the thermal expansion valve 1 body creates a relationship between the power element and the ball seat 14, which creates an orifice within the thermal expansion valve. The stem 11 transfers the movement of the diaphragm 7 via the operating pin to the ball, which results in movement of the ball off the ball seat inside the orifice. When the pressure in the power element 2 decreases, the diaphragm 7 deflects downwardly transferring the motion through the stem 11 and moves the operating pin 12, which pushes down on the ball 13. Movement of the ball allows refrigerant to pass through the valve to the evaporator. Pressure increase in the power element 2 allows the diaphragm to pull up and draw the stem to close the thermal expansion valve. A spring 16 located in an adjustment gland 17 acts upon the operating pin 12 to move the stem 11 to close the thermal expansion value.

FIG. 1 b is the thermal expansion valve of FIG. 1 a where the power element has moved the ball 13 off the ball seat 14. A controlled amount of refrigerant flows through the orifice of the thermal expansion valve and the moves through the angled ball seat 14, the refrigerant exits in flashed condition via the outlet port 5 to the evaporator. When the ball moves off of the ball seat, refrigerant flows through the thermal expansion valve. When the ball 13 moves onto the ball seat 14 it and closes the value so that flow stops. A controlled amount of refrigerant flows through the orifice of the thermal expansion valve into the evaporator. The controlled or metered flow from the thermal expansion valve is temperature and pressure sensitive and can change based on the thermal load of the evaporator. The thermal expansion valve maximizes the efficiency of the evaporator by maintaining a measure of the metered flow.

The power element 2 also includes a filter 18. The filter is positioned between an open end of the power element 2 and the thermal expansion valve body 3 to prevent debris within the vehicle air conditioning system from reaching the underside of the diaphragm. The filter is disposed in the flow path between the evaporator and the diaphragm chamber.

FIG. 2 shows is an exploded view of a power element 2 of the thermal expansion valve. The power element is provided at the top end surface of the body of the thermal expansion valve and may be releasably attached or integrally mounted to the top end surface. The power element includes upper housing portion 8 shaped like an annular domed head and a mating lower housing portion 9 shaped like a mating annular support cup to the upper housing portion. An annular diaphragm 7 having a top and bottom surface is mounted between the upper housing portion and the and lower housing portion. The upper housing 8 and the upper surface of the diaphragm define a head chamber. The lower housing portion 9 and the lower surface of the diaphragm define a diaphragm chamber with the body of the thermal expansion valve. The power element includes a sleeve 10 that passes through the opening in the bottom of the annular lower housing. In addition, a stem 11 is slidably disposed within the sleeve. The stem 11 moves within the sleeve 10 for transfer of motion from the diaphragm an operating pin which is in contact with the ball on the seat. The stem can also include a frictional clip 19 that it threaded through an end of the stem and positioned below the support cup to secure the filter in place. The stem 11 protrudes from the lower housing, coming in contact with a pin to move a ball off of the seat.

A filter 18 is interdisposed around the valve stem 11 positioned adjacent to the open end of the sleeve 10. When the power element 2 is engaged to the body 3 of the thermal expansion valve, the filter 18 is secured between the body of the thermal expansion valve and the bottom opening of the power element creating. The filter is disposed in a flow path between the evaporator and the diaphragm chamber. The filter prevents unwanted debris from entering the vulnerable area on the underside of the diaphragm.

The filter 18 is a collar made of premium grade paper. The paper can be LyTherm® premium grade paper or any other suitable filter paper. Suitable paper must be a lightweight refractory material processed from highly washed, spun, high purity alumina silica fibers formed into a highly flexible sheet. The filter can be of any thickness between 1/16 inch and ¼ inch.

FIG. 3 shows the collar filter 18. The filter is an annular collar that is interdisposed within the sleeve of the power element.

While the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the inventions. The elements of the various embodiments may be incorporated into each of the other species to obtain the benefits of those elements in combination with such other species, and the various beneficial features may be employed in embodiments alone or in combination with each other. Other embodiments and configurations may be devised without departing from the spirit of the inventions and the scope of the appended claims. 

We claim:
 1. A thermal expansion valve for use in an automotive air conditioner comprising: a body including an inlet port fluidly connected to an evaporator and an outlet port fluidly connected to a condenser; a power element having an annular domed upper housing, a mating annular lower housing having an opening in the bottom of the annular lower housing, an annular diaphragm having an upper surface and a lower surface wherein the lower surface of the diaphragm and the annular lower housing define a diaphragm chamber, a sleeve that passes through the opening in the bottom of the annular lower housing and a stem slidably disposed within the sleeve; and a paper filter disposed in a fluid path between the evaporator and the diaphragm chamber.
 2. The thermal expansion valve of claim 1 further including a frictional clip interdisposed around the valve stem for securing the filter.
 3. The thermal expansion valve of claim 1 wherein the filter is made of LyTherm® paper.
 4. A power element for use with a thermal expansion valve of an automotive air conditioner comprising: an annular domed upper housing; a mating annular lower housing having an opening in the bottom of the annular lower housing; an annular diaphragm having an upper surface and a lower surface wherein the lower surface of the diaphragm and the annular lower housing define a diaphragm chamber; a sleeve that passes through the opening in the bottom of the annular lower housing; a stem slidably disposed within the sleeve; and a paper filter interdisposed around the valve stem.
 5. The power element of claim 4 further including a frictional clip interdisposed around the valve stem for securing the filter.
 6. The power element of claim 4 wherein the filter is made of LyTherm® paper. 